1. Field of the Invention
The present invention relates to testing of semiconductor wafers or samples and, more particularly, to determining the mobility of charge carriers in a semiconductor wafer or sample, also know as surface channel mobility.
2. Description of Related Art
For semiconductor devices, a major concern is the so-called surface channel mobility. Conventional mobility measurement methods measure either in-part or completely the bulk mobility which is mostly dominated by lattice and impurity scattering effects. However, the performance of high-speed semiconductor devices is limited by the surface mobility of minority carriers in an inversion layer of the semiconductor wafer or sample. This is heavily dependent on scattering at or adjacent the surface of the semiconductor wafer or sample through interface roughness and Coulomb scattering effects. This is a major concern in current and future semiconductor technology.
Heretofore, surface mobility was measured by creating an inversion layer via a MOS transistor formed in the semiconductor wafer or sample. MOS transistors, however, require complete processing of the semiconductor wafer or sample in order to form the source, drain and gate contacts as well as channel implants and metal definition. This is a time-consuming process and does not provide timely feedback about the quality of the process utilized to form the transistors.
It would, therefore, be desirable to overcome the above drawbacks and others by providing a method and apparatus for testing a semiconductor wafer or sample that avoids the need to form a complete MOS transistor therein. Still other benefits of the invention will be apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.